This is an interesting question.

However what I'll suggest is that a peaceful resolution for Vietnam by 1960 was already too late.

Remember that the goal of North Vietnam (and in some capacity South Vietnam) was unification. If Kennedy had withdrawn (which again is a counterfactual that I won't try to address) the problem is that the withdrawal of the US advisers and aid to Ngo Dinh Diem's government would not necessitate the lack of a conflict, after all Vietnam would still be split.

The other problem is considerations of US policy. Remember that even during Kennedy's time, any Communist country was seen as an entity to oppose. In a twisted way, by Nixon the theorized "Domino Theory" pretty much ends up fulfilling itself. Though the universal applicability of it is debateable, 1960s US foreign policy considerations would most likely be very much opposed to making a deal or even allowing for any "Communist" state. Aside from withdrawal, the other option by 1963 would have been nuclear. Which judging from the Anti-Barry Goldwater Campaigns later on, would have been terribly unpopular.

Anyhow, it's difficult to see an alternative. Remember Lyndon B. Johnson was Kennedy's successor, and by 1963 Diem is killed and replaced by first the Military Council and Minh, then Ngyuen Khanh, and later two more military leaders. The problem is that the answer to this question is that the Vietnam War really wouldn't end earlier.

Remember that the war after 1973 still rages on long after the US withdraws. Though one could argue that the South would capitulate earlier, this doesn't change the fact that in the effort to unify, a large amount of Vietnamese blood would still be spilled. The problem is not what the US could or could not do. The problem is that the 1954 Geneva Convention essentially split a region where a struggle for unification had been already occurring.